Such a highly linear differential transconductance is presented in patent U.S. Pat. No. 5,497,123. This differential transconductance combines two sides each including a single input transconductance. Such a transconductance is a class AB transconductance. This class is advantageous as this is an intermediate between class A, where the consumption is independent of the processed signal, and class B, where there is consumption only when a signal is processed. Advantages of class AB transconductance are also that they present a weak DC and are linear on a large range. Such a transconductance is presented for implementation in a reception chain. As such the transconductance exhibits a low input impedance to match the image rejection filter output impedance. Consequently, the presented transconductance is well adapted to the reception chain as the obtained gain is inversely proportional to the input impedance. A low input impedance is adapted to discrete applications where the input of the transconductance is an off-chip input.
For integrated applications the input impedance needs to be high in order to reduce the consumption. Moreover, such a transconductance is not adapted to the use in transmission chains where a large and linear input impedance is generally asked for upconversion circuits.